Format CONTRIBUTING.md

[ManoelLobo]

Summary

Formats Contributing doc

This PR fixes/implements the following bugs/features

• [ ] Bug
• [ ] Feature
• [ ] Breaking changes

This PR proposes the following changes:

• Formats file with markdown syntax
• Inserts link to cod of conduct file
• Removes repeated content (CoC)

Closing issues

None

[rafaelcastrocouto]

Hi there, thanks for the contribution!

Seems like you deleted more then you intended, are you sure you want to remove all those lines?

🤔Ah, now I get it. It's the same as in the CoC!